Configure statement_timeout for dev/test

In sight of https://gitlab.com/gitlab-org/gitlab/-/issues/251084,
this change configures a `statement_timeout` for both development and
testing environments.

config/database.yml.postgresql

@@ -28,6 +28,8 @@ development:
   username: postgres
   password: "secure password"
   host: localhost
+  variables:
+    statement_timeout: 15s
 
 #
 # Staging specific
@@ -51,3 +53,5 @@ test: &test
   password:
   host: localhost
   prepared_statements: false
+  variables:
+    statement_timeout: 15s

spec/lib/gitlab/database/partitioning_migration_helpers/table_management_helpers_spec.rb

@@ -514,6 +514,7 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::TableManagementHe
         allow(migration).to receive(:table_exists?).with(partitioned_table).and_return(true)
         allow(migration).to receive(:copy_missed_records)
         allow(migration).to receive(:execute).with(/VACUUM/)
+        allow(migration).to receive(:execute).with(/^(RE)?SET/)
       end
 
       it 'finishes remaining jobs for the correct table' do
@@ -567,6 +568,7 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::TableManagementHe
 
         allow(Gitlab::BackgroundMigration).to receive(:steal)
         allow(migration).to receive(:execute).with(/VACUUM/)
+        allow(migration).to receive(:execute).with(/^(RE)?SET/)
       end
 
       it 'idempotently cleans up after failed background migrations' do